Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 5680 | Thousand metric tons | NA |
| 2003 | 5992 | Thousand metric tons | 5.49% |
| 2004 | 6238.583984375 | Thousand metric tons | 4.12% |
| 2005 | 7032.10009765625 | Thousand metric tons | 12.72% |
| 2006 | 8252.765625 | Thousand metric tons | 17.36% |
| 2007 | 10061.34765625 | Thousand metric tons | 21.91% |
| 2008 | 10659 | Thousand metric tons | 5.94% |
| 2009 | 7902 | Thousand metric tons | -25.87% |
| 2010 | 7008 | Thousand metric tons | -11.31% |
| 2011 | 7846 | Thousand metric tons | 11.96% |
| 2012 | 7500 | Thousand metric tons | -4.41% |
